Chapter 4: Data Representation Flashcards Preview

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Flashcards in Chapter 4: Data Representation Deck (65):
1

Bit

A single binary digit: 1 or 0

2

Nibble

4 bits

3

Byte

8 bits

4

Kilobyte

1024 bytes (2¹⁰ bytes)

5

Megabyte

1024 kilobytes (2²⁰ bytes)

6

Gigabyte

1024 megabytes (2³⁰ bytes)

7

Terabyte

1024 gigabytes (2⁴⁰ bytes)

8

What is the order of the various kinds of bytes? (Up to terabytes needed)

1. Byte
2. Kilobyte
3. Megabyte
4. Gigabyte
5. Terabyte
6. Petabyte
7. Exabyte

9

Binary

The base 2 number system, which consists of the digits 1 and 0. Used by computers

10

Why is binary used in computers?

Computers consist of millions of transistors, which are switches that are either on (to store a 1) or off (to store a 0)

11

Denary

Base 10, which uses the digits 0 through 9. The system we use in everyday life

12

Hexadecimal

The base 16 number system, which uses the digits 0-9 and the letters A-F. Used to represent groups of four bits at a time

13

Why is hexadecimal number representation often used?

Hexadecimal is generally easier for people to remember than binary

14

How would you write the denary number 84 in binary?

1010100

15

How would you write the denary number 182 in hexadecimal?

B6

16

How would you write the hexadecimal number FF in denary?

255

17

How would you write the binary number 11111111 in denary?

255

18

How would you write the binary number 01011100 in hexadecimal?

5C

19

How would you write the hexadecimal number 4E in binary?

01001110

20

How would you store a real number in binary?

Store the main part of the number (the mantissa) and the number of times it needs to be multiplied by 10 (the exponent)

21

How would you store a date in binary?

Each date would be stored as a unique number within a certain range of dates and time

22

Character set

The set of symbols that can be represented by a computer, which includes letters, digits, punctuation and control characters

23

How is each character in a character set represented?

Each character is represented by a numerical code stored as a binary integer

24

What are some examples of character sets? (3)

1. ASCII
2. Unicode
3. EBCDIC

25

ASCII

American Standard Code for Information Interchange: a 7-bit character set used by PCs. There is also an extended set that uses 8 bits

26

What is the ASCII code for the space key?

32

27

What is the ASCII code for 'A'?

65

28

What is the ASCII code for 'a'?

97

29

Explain the possible limitations of using the ASCII character set for global communication (4 marks)

1. ASCII uses 7 bits to represent each character
2. This means that it can only represent 128 (2⁷) different characters
3. This is enough to represent the letters and punctuation used in English
4. Some languages have much larger alphabets
5. Global communication would require a character set that contains all of the alphabets in the world - much more than even the 256 in extended ASCII (8 bits)

30

Analogue

A continuously changing wave e.g. natural sound

31

Digital

Data made up of separate values. How data is stored on a computer

32

How is a sound wave converted from analogue to digital? (2)

1. The amplitude (height of the wave) is measured at regular intervals (sampling)
2. These values are stored as a series of binary numbers in a file

33

What do the amplitude and frequency of a sound wave control?

Amplitude: how loud the sound is
Frequency: the sound's pitch

34

What is sound quality affected by? (2)

Sample resolution: the more bits used, the better the accuracy of the sound file
Sample interval: the smaller the interval, the better the quality of playback

35

Sample rate

The number of samples taken per second

36

Sample interval

The time gap between measurements of the sound wave being taken. A different way of expressing the sample rate

37

What is the sample rate of:
1. A CD?
2. A telephone network?

1. 41.1 kHz
2. About 8 kHz

38

Sample resolution OR Bit depth

The number of bits used to store each sample

39

What is the sample resolution of a CD?

16 bit, which produces a good sound quality

40

Sound synthesis

When sound stored in a file is recreated by the computer using a DAC and played through speakers

41

What bit depth and sample rate is becoming more common?

What is the advantage and disadvantage of this?

Bit depth: 24 bit
Sample rate: 96 kHz

Pro: sound quality is better
Con: file sizes are huge

42

What are two commonly used uncompressed audio file types?

1. WAV
2. AIFF

43

Pros and Cons of WAV and AIFF formats (1 | 2)

Pros
1. High sound quality

Cons
1. Large file sizes
2. Do not work well for streaming or downloads

44

Compression

A technique which reduces a file's size by changing its format

45

What are the two types of compression?

1. Lossy: permanently removes data
2. Lossless: no loss of quality, and can be restored to pre-compression state

46

MP3

A commonly used, lossy audio compression format

47

How do MP3s work?

They work by removing frequencies outside the range of human hearing. MP3s can reduce the file size to a twelfth of the original depending on the chosen bitrate

48

Pros and Cons of MP3s (2 | 1)

Pros
1. Ideal for streaming and downloading
2. Can be used easily on portable devices e.g. mobile phones

Cons
1. Musicians claim that even the highest bitrate MP3s do not produce the sound quality of a WAV or AIFF

49

Bitmap image

An image that is stored as a series of values per pixel. Also known as a pixelmap or raster graphics

50

What are three common image file types?

1. JPEG
2. GIF
3. PNG

51

Pixel

Short for "picture element", the smallest component of a bitmap image

52

Colour depth

The number of bits used to represent the colour of a single pixel in a bitmap image

53

Higher colour depth provides...

A broader range of distinct colours

54

What is the colour depth of an image with 4 colours?

2 bits per pixel

55

What is the colour depth of an image stored as a GIF?

8 bits, allowing a total of 256 different colours

56

Resolution

The number of pixels in an image expressed as: number of pixels across * number of pixels down

57

Metadata

Data that serves to provide context or additional information about other data e.g. a file

58

What is the metadata in the case of image files?

The data the computer needs to interpret the image data in the file e.g. image format, resolution, colour depth and image dimensions

59

How does a JPEG compress a bitmap file?

It is a lossy compression format that works by discarding details that are generally undetectable by the human eye

60

What is another way of storing images besides bitmap files?

Vector graphics, which consist of lines with properties such as style, colour, start point and end point. Each of these properties are stored as binary in a file

61

Data

Facts and figures with no context or format to give them meaning

62

Information

Data that has been given meaning

63

ADC

Analogue to Digital Converter: takes real-world analogue information and converts it into a binary representation, which can be stored on a computer

64

DAC

Digital to Analogue Converter: converts digital data into an analogue signal

65

In terms of information and data, what do (1) input devices and (2) output devices do?

1. Input devices take real-world information and store it as data
2. Output devices take data from the computer and present it as information to the user